Conventional mark reading systems have been employed to extract information, such as pencil marks, from a document. These systems typically include a scanner configured to read marks from the document. The scanner creates a digitized representation of the document. The digitized document is then processed by a separate application to evaluate the document. In an assessment environment, this system can be used to score examination responses. For example, many students and other examinees are familiar with the typical response format for answering multiple choice questions which requires the student to fill-in a space (e.g. a circle, square, etc.) associated with the question. Mark reading systems can grade such answer sheets significantly faster and more accurately than a human grader. However, conventional mark reading systems are limited by the accuracy with which the document is digitized. Increased accuracy is available with more sophisticated and more expensive systems. When a high degree of accuracy is required, expensive scanning equipment can be purchased which will provide a digitized representation of the document within most accepted error rates. However, in addition to the expense associated with such systems, they may not be easily configured to alternate environments where differing accuracy levels are required. When accuracy in the digitizing process is sacrificed, such systems often improperly grade test answers. For example, the systems may not recognize properly marked target areas that are incompletely filled or in which the pencil marking is lighter than a threshold value. Moreover, the systems may recognize stray marks and erasures as incorrect answers when a test taker did not intend such an answer.
A particularly egregious error may result when a test taker properly marks a correct answer for a question, but a mark reading system recognizes a stray mark or erasure as an incorrect answer for the same question. In this case, although the test taker correctly answered the question, the test taker would not receive credit because the system would report that the test taker provided two answers. As such, the test taker may be penalized because of the medium in which the test is presented rather than the substantive material on which the test is based.
What is needed is an improved image mark recognition system that can accurately evaluate the marks on a document to be digitized which is both cost effective and independent of the hardware being used to scan the document.